Background & Aims: In the past serum creatinine concentration was used as one of the important markers for early detection of kidney disorders, however recent studies suggest serum cystatin C to be a better marker. Therefore in this study we compared the diagnostic value of cystatin C with serum creatinine to evaluate kidney function in patients with high blood pressure.

Materials & Methods : This clinical trial study was conducted on high blood pressure patients referring to Mehrad hospital during 1387-1389 for checking their kidney function. Cobasmira automated analyzer was used to determine serum creatinine. The serum cystatin C was measured using ELISA method. The glomerular filtration rate was determined by measuring 24hr creatinine clearance. Positive and negative predictive value, sensitivity and specificity of cystatin C and creatinine were determined.

Results : We studied 35 patients with high blood pressure (20 men and 15 women mean age, 49±11). This research work showed that positive predictive value and negative predictive value of creatinine were 94.3% and 31% respectively. And for cystatin C, were 92.3% and 44% respectively.

The false positive and negative result for serum creatinine method were 2.8% and 31.4% and for cystatin C were 5.7% and 14.2% respectively.

Total accuracy of cystatin C was 90% and creatinine was 65.8%. Finally based on results obtained from this study cystatin C had a sensitivity of 82 % and specificity of 57% and serum creatinine had sensitivity of 62 % and specificity of 41% for detecting crcl<78 ml/min/1.73m2.

Conclusion : It seems that measurement of serum cystatin C can be applied to detect the reduction of kidney function in the primary stages of kidney disorder.